1. Field of the Invention
This invention generally relates to diamond bonded constructions and, more particularly, to diamond bonded compact constructions that are specially engineered having a diamond body bonded to a substrate, wherein the diamond body includes multi-sintered polycrystalline diamond to provide a construction having reduced residual stresses and cracks to provide improved performance properties and service life when compared to conventional diamond bonded constructions.
2. Background of the Invention
The use of constructions comprising a body formed from ultra-hard materials such as diamond, polycrystalline diamond (PCD), cubic boron nitride (cBN), polycrystalline cubic boron nitride (PcBN) are well known in the art. Examples of such constructions may be found in the form of cutting elements comprising an ultra-hard component or body that is joined to a metallic component or substrate. In such cutting elements, the wear or cutting portion is formed from the ultra-hard component and the metallic portion is provided for the purpose of attaching the cutting element to a desired wear and/or cutting device. In such known constructions, the ultra-hard component may be formed from those ultra-hard materials described above that provide a high level of wear and/or abrasion resistance that is greater than that of the metallic component.
The use of PCD as an ultra-hard material for forming such constructions is well known in the art. PCD is formed by subjecting a volume of diamond grains to high pressure/high temperature (HPHT) conditions in the presence of a suitable catalyst material, such as a solvent catalyst metal selected from Group VIII of the Periodic table. Oftentimes, the source of the solvent catalyst material used to form PCD is the substrate, wherein the solvent catalyst material is present as a constituent of the substrate that migrates therefrom and infiltrates into the adjacent diamond body during HPHT processing. The resulting construction is a PCD compact comprising the PCD body joined to the substrate.
An issue known to exist with such conventional PCD compact constructions is the presence of relatively high levels of residual stress in the diamond body and/or in the substrate adjacent the interface between the two. This residual stress may be created during the HPHT process used to form the PCD body and/or during the brazing process that is used to attach the compact to an end-use device, such as a bit used for drilling subterranean formations. Such high levels of residual stress exist in PCD compacts comprising a PCD body formed from relatively fine-sized diamond grains and having a relatively low metal content, where higher pressures are needed to achieve better sintering. The use of such higher sintering pressures is believed to contribute to the higher level of residual stress present in such PCD compact constructions. Such residual stress may cause cracking to occur within the diamond body and/or substrate when the compact is attached to an end-use device and/or placed in a wear or cutting operation, and may result in premature compact failure.
It is, therefore, desired that diamond bonded constructions be constructed in a manner that provides a reduced or eliminated degree of residual stress when compared to conventional PCD compact constructions. It is also desired that such diamond body constructions, and methods useful for making the same, facilitate the formation of diamond bonded constructions comprising diamond bonded bodies formed from relatively fine-sized diamond grains and having a relatively low metal content. It is further desired that such diamond bonded constructions be made in a manner that does not sacrifice desired properties of wear resistance, abrasion resistance, impact resistance, and fracture toughness when compared to conventional PCD compact constructions. It is still further desired that such diamond bonded constructions be produced in a manner that is efficient and does not involve the use of exotic materials and/or techniques.